Agribusiness applications (agriculture and aquaculture) are particularly attractive because they require
marketable crops have been raised in geothermally heated greenhouses in Tunisia, Hungary, Russia, New Zealand, Japan, Iceland, China, and the United States. These include vegetables such as cucumbers and tomatoes, flowers (both potted and bedded), house plants, tree seedlings, and cacti. Using geothermal energy for heating reduces operating costs (which can account for 35% of the product cost) and allows operation in colder climates where commercial greenhouses would not normally be economical.
The use of geothermal energy for raising catfish, shrimp, tilapia, eels, and tropical fish has produced crops faster than by conventional solar heating. Using geothermal heat allows better control of pond temperatures, thus optimizing growth (Fig. 7). Fish
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FIGURE 7 Effect of temperature on animal and fish growth.
breeding has been successful in Japan, China, and the United States. A very successful prawn-raising operation, producing 400 tons of giant Malaysian freshwater prawns per year at $17-27/kg, has been developed near the Wairakei geothermal field in New Zealand. The most important factors to consider are the quality of the water and disease. If geothermal water is used directly, concentrations of dissolved heavy metals, flurorides, chlorides, arsenic, and boron must be considered.
Livestock-raising facilities can encourage the growth of domestic animals by a controlled heating and cooling environment. Use of an indoor facility can lower the mortality rate of newborns, enhance growth rates, control diseases, increase litter size, make waste management and collection easier, and, in most cases, improve the quality of the product. Geothermal fluids can also be used for cleaning, sanitizing, and drying of animal shelters and waste as well as assisting in the production of biogas from the waste.
Although the Lindal diagram shows many potential industrial and process applications of geothermal energy, the world’s uses are relatively few. The oldest industrial use is in Larderello, Italy, where boric acid and other borate compounds have been extracted from geothermal brines since 1790. Today, the two largest industrial uses are the diatomaceous earthdrying plant in northern Iceland and a pulp, paper, and wood processing plant in Kawerau, New Zealand. Notable U. S. examples are two onion dehydration plants in northern Nevada and a sewage digestion facility in San Bernardino, California. Alcohol fuel production has been attempted in the United States; however, the economics were marginal and thus the industry has not been successful.
Drying and dehydration are important moderate – temperature uses of geothermal energy. Various
vegetable and fruit products are feasible with the use of continuous belt conveyors (Fig. 8) or batch (truck) dryers with air temperatures from 40 to 100°C. Geothermally drying alfalfa, onions, pears, apples, and seaweed is an example of this type of direct use. A new development in the use of geothermal fluids is the enhanced heap leaching of precious metals in Nevada by applying heat to the cyanide process. Using geothermal energy increases the efficiency of the process and extends the production into the winter months.